Respiratory syncytial virus vaccine

ABSTRACT

Described is a vaccine against Respiratory Syncytial Virus (RSV). More specifically, described is a recombinant subunit vaccine comprising the ectodomain of the RSV-encoded Small Hydrophobic (SH) protein. The ectodomain of SH is referred to as SHe. The ectodomain is typically presented as an oligomer, or pentamer. Further described are antibodies, raised against the ectodomain or specific for the ectodomain, and their use for protecting a subject against RSV infection and/or for treatment of an infected subject.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/144,007, filed Sep. 27, 2018, which is a division of U.S. patentapplication Ser. No. 15/197,001, filed Jun. 29, 2016, now U.S. Pat. No.10,117,926, which is a continuation of U.S. patent application Ser. No.13/885,388, filed Aug. 7, 2013, now U.S. Pat. No. 9,409,973, which is a35 U.S.C. § 371 filing of International Patent Application No.PCT/EP2011/070161, filed Nov. 15, 2011, which claims priority to GreatBritain Patent Application No. 1019240.9, filed Nov. 15, 2010, and U.S.Provisional Patent Application Ser. No. 61/458,012, filed Nov. 15, 2010.Each of these priority applications is incorporated by reference hereinin their entirety.

TECHNICAL FIELD

The disclosure relates generally to biotechnology and medicine and moreparticulary to a vaccine against Respiratory Syncytial Virus (RSV). Morespecifically, it relates to a recombinant subunit vaccine comprising theectodomain of the RSV-encoded Small Hydrophobic (SH) protein. Theectodomain of SH is referred to as SHe. The ectodomain may be presentedas an oligomer, even more preferably, as a pentamer. The disclosurerelates further to antibodies, raised against the ectodomain or specificfor the ectodomain, and their use for protecting a subject against RSVinfection and/or for treatment of an infected subject.

BACKGROUND

RSV infection is the leading cause of infant hospitalization inindustrialized countries. Following primary RSV infection, whichgenerally occurs under the age of 2 years, immunity to RSV remainsincomplete, and reinfection can occur. Furthermore, RSV can causeserious disease in the elderly and is, in general, associated withhigher mortality than influenza A in non-pandemic years (Falsey et al.,1995). The WHO-estimated global annual infection rate in the humanpopulation is estimated at 64 million cases, with a mortality figure of160000; in the US alone, from 85000 to 144000 infants are hospitalizedeach year as a consequence of RSV infection (on the World Wide Web atwho.int/vaccine research/diseases/ari/en/index2.html update 2009).

RSV belongs to the family Paramyxoviridae, subfamily Pneumovirinae,genus Pneumovirus; in human, there are two subgroups, A and B. Apartfrom the human RSV, there is a bovine variant. The genome of human RSVis approximately 15200 nucleotides long and is a negative-sense RNAmolecule. The RSV genome encodes 11 known proteins: Glycoprotein (G),Fusion protein (F), Small hydrophobic protein (SH), Nucleoprotein (N),Phosphoprotein (P), Large protein (L), Matrix protein (M), M2 ORF-1protein (M2-1), M2 ORF-2 protein (M2-2), Nonstructural protein 1 (NS1)and Nonstructural protein 2 (NS2). G, F and SH are transmembrane surfaceproteins; N, P, L, M, M2-1 are nucleocapsid associated proteins; and NS1and NS2 are non-structural proteins. The status of M2-2 as a structuralor nonstructural protein is unknown. (Hacking and Hull, 2002.) The RSVsubgroups show differences in the antigenic properties of the G, F, Nand P proteins (Ogra, 2004).

RSV infection is followed by the formation of specific IgG and IgAantibodies detectable in the serum and some other body fluids. Severalstudies have demonstrated that antibody responses are mainly directed tothe major RSV transmembrane proteins F and G; only F- and G-specificantibodies are known to have in vitro RSV-neutralizing activity.Antibody responses to the F protein are often cross-reactive between theA and B subgroups, whereas antibody responses to the G protein aresubgroup specific (Orga, 2004). Contrary to F and G, the transmembraneprotein SH is considered as non-immunogenic (Gimenez et al., 1987;Tsutsumi et al., 1989) and in some vaccine candidates, SH has even beendeleted in order to obtain a non-revertible attenuated vaccine (Karronet al., 2005).

Development of vaccines to prevent RSV infection has been complicated bythe fact that host immune responses appear to play a significant role inthe pathogenesis of the disease. Early attempts at vaccinating childrenwith formalin-inactivated RSV showed that vaccinated childrenexperienced a more severe disease on subsequent exposure to the virus ascompared to the unvaccinated controls (Kapikian et al., 1969). Liveattenuated vaccines have been tested, but show often over- orunderattenuation in clinical studies (Murata, 2009).

Subunit vaccines using one immunogenic protein or a combination ofimmunogenic proteins are considered safer, because they are unable torevert or mutate to a virulent virus. Candidate vaccines based onpurified F protein have been developed and were tested in rodents,cotton rats, and humans, and were shown to be safe, but only moderatelyimmunogenic (Falsey and Walsh, 1996; Falsey and Walsh, 1997; Groothuiset al., 1998). In a similar vein, clinical trials with a mixture ofF-,G- and M-proteins have been discontinued in phase II (ADISinsightClinical database). An alternative approach consisted of a recombinantgenetic fusion of the antigenic domain of human RSV G protein to theC-terminal end of the albumin-binding domain of the streptococcal Gprotein (BBG2Na; Power et al., 2001). BBG2Na was investigated up to aphase III clinical trial in healthy volunteers, but the trial had to bestopped due to the appearance of unexpected type 3 hypersensitivity sideeffects (purpura) in some immunized volunteers (Meyer et al., 2008).

A recent development is the use of chimeric recombinant viruses asvector for RSV antigens. A chimeric recombinant bovine/humanparainfluenzavirus type 3 (rB/HPIV-3) was engineered by substituting ina BPIV-3 genome the F and HN genes by the homologous genes from HPIBV-3.The resulting chimeric rB/HPIV-3 strain was then used to express theHRSV F and G genes (Schmidt et al., 2002). This vaccine is currentlyunder clinical investigation.

Only a limited number of prevention and treatment options are availablefor the severe disease caused by RSV. The most widely used interventionis based on passive immunoprophylaxis with a humanized monoclonalantibody that is derived from mouse monoclonal antibody 1129 (Beeler andvan Wyke Coelingh, 1989). This antibody is specific for RSV F proteinand neutralizes subgroup A and B viruses. The recombinant humanizedantibody 1129 is known as palivizumab (also known as Synagis) and isused for prophylactic therapy of infants that are at high risk ofdeveloping complications upon RSV infection. The antibody isadministered intramuscularly on a monthly basis in order to lower therisk of RSV infection in infants at risk due to prematurity, chroniclung disease, or hemodynamically significant congenital heart disease(Bocchini et al., 2009). Some studies have reported acceptablecost-effectiveness ratios for RSV prophylaxis with palivizumab (Prescottet al., 2010).

SUMMARY OF THE DISCLOSURE

As there is no approved vaccine on the market, there is still an unmetneed for development and availability of a safe and efficient RSVvaccine. Surprisingly, we found that the extracellular part (ectodomain)of the small hydrophobic protein SH, referred to as SHe, can be usedsafely for vaccination against RSV infection, especially when it ispresented on a carrier as an oligomer, such as a pentamer. Furthermore,polyclonal or monoclonal antibodies, directed against SHe, can also beused prophylactically or therapeutically for prevention or treatment ofRSV infection, respectively.

Described is an immunogenic composition comprising the ectodomain of thesmall hydrophobic (SH) protein of a Respiratory Syncytial Virus (RSV),and a carrier. In one embodiment, RSV is either a human subgroup A or ahuman subgroup B strain; in another embodiment, RSV is bovine RSV. TheSH protein is known to the person skilled in the art, and contains 64(RSV subgroup A), 65 (RSV subgroup B) amino acid residues or 81, 77 or72 amino acid residues for bovine RSV. In one embodiment, the ectodomainof SH (SHe) consists of the 23 carboxy terminal amino acids for subgroupA (SEQ ID NO: 1), and of the 24 carboxy terminal amino acids forsubgroup B (SEQ ID NO:2). The sequence of the ectodomain may be selectedfrom the group consisting of SEQ ID NO:1 (ectodomain subgroup A) and SEQID No 2 (ectodomain subgroup B), or a variant thereof. A “variant,” asused herein, means that the sequence can carry one or more mutations,such as deletions, insertions or substitutions. In certain embodiments,the mutations are substitutions. Even more preferably, the variant has80% identities, preferably 85% identities, even more preferably, 90%identities, most preferably 95% identities, as measured in a BLASTpalignment (Altschul et al., 1997). Preferably, the variant comprises thesequence NKL C/S E Y/H KIN XF (SEQ ID NO:3). Preferred variants arelisted in SEQ ID NO:4-SEQ ID NO: 16. In another preferred embodiment,the ectodomain consists of SEQ ID NO:17 (ectodomain of Bovine RSV SH) ora variant thereof, as defined above. Preferably, the variant comprisesthe sequence NKLCXXXXXHTNSL (SEQ ID NO:18). Preferred variants arelisted in SEQ ID NOS:19-30.

A carrier molecule is a molecule that is heterologous to the SH protein;a carrier can be any carrier known to the person skilled in the art assuitable for the presentation of an antigen and includes, but is notlimited to, virus-like particles such as HBcore (Whitacre et al., 2009),and other VLPs derived from assembling virus capsid or coat proteins.Any other molecular construct can also be used, provided it canefficiently present antigens to the immune system, such as thepentameric Cartilage Oligomeric Matrix Protein (comp; McFarlane et al.,2009), Thromobospondins 3 and 4 (Malashkevich et al., 1996), the Bsubunit of bacterial AB5 type toxins (e.g., subunit of Cholera toxin orE. coli heat labile toxin; Williams et al., 2006), a pentamerictryptophan-zipper (Liu et al., 2004), a pentameric phenylalanine-zipper(Liu et al., 2006) or a tetrameric GCN4-derived leuzine zipper (tGCN4,De Filette et al., 2008) and Lpp-56 (Shu et al., 2000). The carrier canbe of a proteinaceous nature, as well as of a non-proteinaceous nature.Examples of non-proteinaceous nature carriers are, as a non-limitingexample, liposomes, CLIPSm4 constructs (Timmerman et al., 2007) andtrimethyl chitosan (Shifter et al., 2010). Preferably, the carrierpresents the SHe as an oligomer, even more preferably, as a pentamer, bypresenting multiple SHe molecules on one scaffold, by presenting one SHeon a multimerizing scaffold, or by a combination of both. The SHeoligomer may be presented as a linear repeated structure, or asindividual SHe units forming an oligomeric complex, or as a combinationof both. The carrier may be an oligomeric carrier (dimeric, up todecameric) or a pentameric carrier. In one specific embodiment, thetransmembrane domain of SH, which may be without the cytoplasmic domain,can be used as oligomerizing domain, optionally further fused or linkedto a carrier.

Not all carrier molecules should be loaded by SHe. Indeed, as anon-limiting example, one can imagine that only 5 units of a hexamericcarrier are loaded with SHe, thereby presenting a pentameric SHe complexon a hexameric carrier complex. The ectodomain can be genetically linkedto the carrier, forming a fusion protein; both domains may be directlyfused, or they may be linked by a hinge sequence or a spacer sequence.As used here, in a genetically fused construct, a hinge sequence is anamino acid sequence that links two domains together; the sequence linksthe two domains in a flexible way; the hinge sequence is shorter than150 amino acids, even more preferably, shorter than 100 amino acids,even more preferably, shorter than 50 amino acids, most preferably,shorter than 20 amino acids. A “spacer,” as used herein, indicates ashort hinge sequence shorter than 15 amino acids. In one embodiment, ahinge sequence comprises the sequence (Gly-Ser)n with n equal to one, 2,3, . . . 20. In another embodiment, the hinge of immunoglobulin genes,such as the hinge region of human IgG1, is used as a hinge sequence. Inthe case of a genetic linkage, the linkage may occur at the aminoterminal end of the SHe, as well as at the carboxy terminal end.

Alternatively, the ectodomain is chemically linked to the earner.Chemical linkage is known to the person skilled in the art, andincludes, but is not limited to, peptides that are conjugated to thecarrier by covalently joining peptides to reactive sites on the surfaceof the carrier. The resulting structure is a conjugate. A reactive siteon the surface of the carrier is a site that is chemically active orthat can be activated and is sterically accessible for covalent joiningwith a peptide. A preferred reactive site is the epsilon nitrogen of theamino acid lysine. Covalently joined refers to the presence of acovalent linkage that is stable to hydrolysis under physiologicalconditions. The covalent linkage may be stable to other reactions thatmay occur under physiological conditions including adduct formation,oxidation, and reduction. Often, the linkage of an antigenic peptide toa carrier is achieved using bifunctional reagents (Hermanson, 1996). Anysuitable residue in the SHe may be used for linkage to the chemicalearner; preferably, SHe is linked to the carrier by its amino terminalor carboxy terminal end.

In still another embodiment, the ectodomain is linked to the carrier bya non-covalent interaction, such as, but not limited to, hydrophobicinteractions, cooperative H-bond interactions, or Van der Waalsinteractions.

Also described is the use of an immunogenic composition hereof as avaccine. Still further described is the use of an immunogeniccomposition hereof for the preparation of a vaccine for the protectionagainst RSV infection. The RSV may be selected from the group consistingof RSV subgroup A and RSV subgroup B. The vaccine can be administratedto the subject to be treated by any route known to the person skilled inthe art including, but not limited to, intranasal, intraperitoneal,intramuscular and intradermal administration. Preferably, there is noenhancement of the disease symptoms upon RSV infection aftervaccination. The vaccine can be for animal or for human use. A preferredanimal use is for protection of cattle or other Bovidae by vaccinationagainst bovine respiratory viruses related to human RSV, such as, butnot limited to, Bovine RSV. Protection against RSV infection covers bothprophylactic and therapeutic uses. More particularly, a preferred use ofthe vaccine is for prophylactic purposes. “Preparation of a vaccine,” asused herein, means that the immunogenic composition hereof may beoptimized by addition of suitable excipients, or it may be formulatedfor, as a non-limiting example, increasing the shelflife or improvingthe pharmaceutical characteristics of the vaccine.

Described is a vaccine comprising an immunogenic composition hereof, ora combination of immunogenic compositions hereof. Indeed, as anon-limiting example, immunogenic compositions comprising SHe of RSVsubgroup A and SHe of RSV subgroup B may be mixed to obtain a vaccinewith a broader specificity. The vaccine can be for human or forveterinary use. Apart from the immunogenic composition, the vaccine maycomprise one or more other compounds, such as an adjuvant. The vaccinemay be a vaccine for the protection of humans against RSV infection or,in animals, against animal respiratory viruses related to human RSV,such as, but not limited to, bovine RSV.

Described is the use of an immunogenic composition hereof for thedetection and/or purification of antibodies, directed against theectodomain of RSV. Such antibodies may be isolated after vaccinating asubject with the immunogenic composition of the invention;alternatively, similar antibodies and/or antibody-producing cells canalso be obtained from an RSV-infected human or animal subject, and,after proper development known in the art, used for production ofSHe-specific antibodies, preferably human-type antibodies that can beused for prophylactic or therapeutic purposes as described above.

Described is a method for the production of blood, plasma and/or serumfrom an animal, the blood, plasma and/or serum comprising one or moreantibodies or cells producing antibodies against the SHe domain of RSV,the method comprising (a) delivering an immunogenic composition hereofto the animal and (b) obtaining blood, plasma and/or serum from theanimal, wherein the blood, plasma and/or serum comprises one or moreantibodies or cells producing antibodies against the SHe domain of RSV,or cells producing the antibodies. Preferably, the animal is a non-humananimal. As used herein, “plasma” is the liquid fraction of the bloodafter removal of the blood cells; serum is plasma after removal offibrinogen and other blood clotting factors. As indicated above,specific anti-SHe antibodies may be isolated using the immunogeniccomposition hereof.

Described is the use of blood, plasma and/or serum containingRSV-antibodies and obtained with the method hereof for protectionagainst RSV infection and/or treatment of RSV infection. As mentionedabove, protection against RSV infection covers both the prophylactic andtherapeutic use. Indeed, the antibody-comprising serum can beadministered to a human or an animal, thereby providing passive immunityagainst the RSV infection. The serum may be part of a pharmaceuticalcomposition comprising the serum, wherein the serum is formulated and/ormixed with a suitable excipient. Described is a pharmaceuticalcomposition comprising a serum obtained with the method hereof.

Described is an RSV-inhibiting monoclonal antibody, directed against theectodomain of the RSV SH-protein. “RSV-inhibiting,” as used herein,means that, upon infection, the lung virus titer is lower in treatedanimals compared to the non-treated animals, as measured in a suitableanimal model. Preferably, the monoclonal antibody is a human orhumanized monoclonal antibody.

Described is a pharmaceutical composition comprising a monoclonalantibody directed against the ectodomain of the RSV SH-protein, hereof.Indeed, an organ of an immunized non-human animal, preferably the spleenof the animal, or a blood sample from an immunized animal or humansubject, can be used as starting material for the production ofmonoclonal antibodies and derivatives such as, but not limited to,single-chain antibodies, multivalent antibodies, or antibodies linked toantiviral compounds. The monoclonal antibodies and derivatives are usedfor passive immunization or for treatment of RSV infection.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1: Panel A, The amino acid sequences of the subtype A human RSV(hRSV) SH ectodomain (SEQ ID NO:1), of the subtype B human RSV SHectodomain (SEQ ID NO:2), and of the bovine RSV (bRSV) SH ectodomain(SEQ ID NO:17). Panel B, The amino acid sequence of Flag-COMPcc-SHe (SEQID NO:35). The first nine amino acids represent the N-terminal Flag-tag.The amino acids (AA) in italic font represent the coiled coil domain ofrat COMP (AA 25-72). The underlined AA represent the ectodomain of theRSV A small hydrophobic protein (SHe). Panel C, Schematic representationof Flag-COMPcc-SHe pentameric protein. Panel D, Schematic representationof COMPcc-SHe pentameric protein.

FIG. 2: Purification and determination of the relative molecular mass ofFlag-COMPcc-SHe. Panel A, Elution curves of aldolase (1), conalbumin(2), albumin (3), chymotrypsinogen (4), ribonuclease A (5) andFlag-COMPcc-SHe (6 en 7) upon gel filtration on a Superdex 75 column.Panel B, Coomassie blue staining of a SDS-PAGE analysis ofFlag-COMPcc-SHe after gel filtration (peak 6 of panel A). Panel C,overview of the proteins used to calibrate the gel filtration column,their relative molecular weight (Mr), the Volume at which they elutedfrom the column (Ve) and the calculated Kay (Kay=(Ve−VO)/(Vtot−VO), withVO the column void volume=9.05 and Vtot=the column bed volume=19.816).The Mr of Flag-COMPcc-SHe present in peak 6 was calculated based on itsVe and the calibration curve presented in panel D. Panel D, Thecalibration curve of the Superdex 75 gel filtration column used topurify pentameric Flag-COMPcc-SHe.

FIG. 3: Vaccination of Balb/c mice with Flag-COMPcc-SHe in combinationwith LTR192G induces SHe-specific antibodies. Panels A, B and C,ELISA-based determination of the SHe peptide-specific IgG antibodiestiters present in the pooled sera of mice after the first, second orthird immunization with the indicated vaccines. Panel D, SHepeptide-specific IgG, IgG1 and IgG2a antibodies present in the pooledsera of mice that were vaccinated with PBS, M2e-tGCN4/LTR192G orFlag-COMPcc-SHe/LTR192G.

FIG. 4: Flag-COMPcc-SHe vaccination, as in legend of FIG. 3, inducesantibodies that can recognize the SH-ectodomain on the surface of cells.Panel A, Flow cytometric analysis of GFP and RSV SH-expressing HEK293Tcells stained by different dilutions of serum of Flag-COMPcc-SHevaccinated mice. Panel B, Flow cytometric analysis of GFP and RSVSH-expressing HEK cells stained by serum from Flag-COMPcc-SHe orM2e-tGCN4 (negative control) vaccinated mice. Panel C, Flow cytometricanalysis of GFP and Luciferase-expressing HEK cells stained by serumfrom Flag-COMPcc-SHe or M2e-tGCN4 vaccinated mice.

FIG. 5: Flag-COMPcc-SHe vaccination inhibits RSV replication. Four daysafter challenge, mice of the indicated groups were sacrificed todetermine viral lung titer by plaque assay. The graph shows the numberof plaque-forming units per lung of each mouse. The detection limit ofthe plaque assay is 10 PFU per lung. The difference in RSV lung titerbetween the Flag-COMPcc-SHe-vaccinated and the M2e-tGCN4-vaccinated micewas highly significant (*** p::::, 0.0005).

FIG. 6: Flag-COMPcc-SHe vaccination does not induce enhanced diseaseupon RSV infection. The graph shows the relative body weight of eachmouse, calculated as the ratio between the weight at the day ofsacrifice (four days after infection) and the weight at the day of viralinfection, multiplied by 100.

FIG. 7: Chemical linkage of SHe(cc4s) peptides to the immunodominantloops of mHBc virus-like particles. Coomassie blue stained SDS-PAGEanalysis of mHBc at the different stages of chemical linkage asindicated above the gel: mHBc=purified mHBc, mHBc-SMBS+sMBS=mHBc afteraddition of the chemical linker Sulfo-MBS, mHBc-SMBS=mHBc-SMBS aftersize exclusion chromatography, mHBC-SHe(cc4s)+SHe(cc4s)=purifiedmHBc-SMBS after incubation with SHe(cc4s) peptide, mHBC-SHe(cc4s)=SHelinked to mHBc VLPs after purification by size exclusion chromatography.

FIG. 8: mHBc-SHe(cc4s) retains its VLP conformation. The graphrepresents the size distribution of mHBc-SHe(cc4s) and thewell-described M2e-mBHc VLP 1604 as determined by dynamic lightscattering. The size distribution is expressed in function of theVolume.

FIG. 9: Purification of SHe-tGCN4. SDS-PAGE analysis followed byCoomassie blue staining of SHe-tGCN4 after purification by a series ofcolumn chromatographic steps: anion exchange, hydrophobic interactionand gel filtration chromatography. The left and right panels representSDS-PAGE analysis under reducing (in the presence ofbeta-mercaptoethanol) or non-reducing (in the absence ofbeta-mercaptoethanol), respectively. The arrows indicate monomeric anddimeric SHe-tGCN4 proteins.

FIG. 10: Both SHe-tGCN4 and mHBc-SHe(cc4s) vaccination induce SHepeptide-specific antibodies. Panel A, The figure represents the titersof SHe-specific IgG antibodies present in the pooled sera of mice of theindicated groups after the first immunization, the first boostimmunization (boost) and the second boost immunization (boost 2), asanalyzed by SHe peptide ELISA. Panel B, The figure represents the titersof SHe-specific IgG, IgG1 and IgG2a antibodies present in the pooledsera of mice of the indicated groups after the second boostimmunization, as determined by peptide ELISA.

FIG. 11: Both SHe-tGCN4 and mHBc-SHe(cc4s) vaccination decreasepulmonary RSV replication. Three days after challenge, the mice weresacrificed to determine the viral lung titer by QRt-PCR. The upper graphrepresents the relative expression of genomic RSV RNA, normalized to theGADPH mRNA levels present in the samples of each mouse in the indicatedgroups. The statistical differences between the vaccinated groups areindicated. The lower panel (B) is identical to the upper panel (A) butalso includes the results from the PBS-vaccinated mice.

FIG. 12: Neither mHBc-SHe(cc₄s) nor tGCN4-SHe vaccination inducesenhanced disease upon RSV infection. The figure shows the averagerelative bodyweight of each indicated group of mice, calculated as theratio between the weight at the indicated day and the weight at the dayof infection (day 0), multiplied by 100.

FIG. 13: 3D11 and 3G8 are two SHe-specific monoclonal Abs of,respectively, the IgG1 and IgG2a subtype. The graph shows the binding ofdilution series of 1 !Jgi!Jl of the 3D11 and 3G8 monoclonal antibodiesto SHe peptide in an ELISA assay detected by either mouse IgG1- or mouseIgG2a-specific secondary antibodies.

FIG. 14: 3D11 and 3G8 mAbs bind to the RSV SH ectodomain on living cellsexpressing the RSV SH protein on their cell surface. Panel A, Flowcytometric analysis of the binding of 3D11 and 3G8 mAbs and respectiveisotype matched control antibodies to Hek293T cells expressing GFP andthe RSV SH protein. Panel B, Flow cytometric analysis of the binding of3D11 and 3G8 mAbs to Hek293T cells expressing GFP in combination witheither the RSV SH protein or a control protein (luciferase).

FIG. 15: Binding of 3D11 and 3G8 mAbs to the cell surface ofRSV-infected cells. Vero cells were infected with 0.5 MO1 of RSV A2.Twenty hours after transfection, the cells were fixed, permeabilized andstained with 3D11 or 3G8 in combination with a polyclonal anti-RSV serumto identify the infected and non-infected cells. The upper panelsrepresent an overview of the immunostaining (DAPI nuclear stain, 3D11and polyclonal RSV serum), including infected and non-infected cells.The lower panels represent confocal images of an infected cell,indicated in the upper panel.

FIG. 16: Passive immunization with SHe-specific monoclonal antibodiesreduced RSV infection in mice. Balb/c mice were treated with PBS,SHe-specific 3G8 mAbs or isotype control antibodies via intranasaladministration one day before and one day after RSV challenge. Eachsymbol represents the lung virus titer of individual mice, four daysafter RSV challenge(** p::; 0.01).

FIG. 17: Intraperitoneal vaccination of Balb/c mtce with KLH-SHe incombination with Freund's Incomplete Adjuvant induces SHe-specificantibodies and reduces RSV replication. Panel A, ELISA-baseddetermination of the SHe-specific IgG antibodies present in the sera ofindividual mice after the third immunization (boost 2) with theindicated vaccines. Panel B, ELISA-based determination of SHe-specificIgG, IgG1 and IgG2a antibodies present in the pooled sera of mice thatwere vaccinated with the KLH-SHe. Panel C, KLH-SHe vaccination does notinduce enhanced disease upon RSV infection. The graph shows the relativebody weight of each mouse, calculated as the ratio between the weight onthe day of sacrifice (five days after infection) and the weight on theday of viral infection, multiplied by 100. The difference in relativebody weight between the KLH-SHe-vaccinated and the KLH-vaccinated miceis significant (p:::; 0.005, Mann-Whitney U test). Panel D, KLH-SHevaccination impairs RSV replication. Five days after challenge with 10⁶PFU RSV, the mice of the indicated groups were sacrificed and lunghomogenates were prepared to determine the viral lung titer by plaqueassay. The graph shows the number of plaque forming units per lung ofeach mouse. The detection limit of the plaque assay is 20 PFU per lung.The difference in RSV lung titer between the KLH-SHe-vaccinated and theKLH-vaccinated mice is significant (p:::; 0.005, Mann-Whitney U test).Panel E, For KLH-SHe-vaccinated mice, high titers of SHe-specific serumantibodies strongly correlate with reduction of RSV replication. Thegraph shows for each KLH-SHe-vaccinated mouse, the titer of SHe-specificserum IgG antibodies and the number of PFU/lung that could be detectedfive days after infection. In the graph, the best fitting curve (power)and its R2 (coefficient of determination) are shown.

FIG. 18: Intranasal vaccination of Balb/c mice with KLH-SHe incombination with LTR192G induces SHe-specific antibodies and reduces RSVreplication. Panel A, ELISA-based determination of the SHe-specific IgGantibodies present in the sera of individual mice after the thirdimmunization (boost 2) with the indicated vaccines. Panel B, ELISA-baseddetermination of the SHe-specific IgG, IgG1 and IgG2a antibodies presentin the pooled sera of mice that were vaccinated with KLH-SHe. Panels Cand D, ELISA-based determination of the SHe-specific IgG and IgAantibodies present in the BAL fluid of individual mice that werevaccinated with the indicated vaccines and infected with RSV five daybefore the collection of BAL fluid. Panel E, KLH-SHe vaccination impairsRSV replication. Five days after challenge with 10⁶ PFU RSV, the mice ofthe indicated groups were sacrificed to determine viral lung titer byplaque assay. The graph shows the number of plaque forming units perlung of each mouse. The detection limit of the plaque assay is 20 PFUper lung. The difference in RSV lung titer between theKLH-SHe-vaccinated and the KLH-vaccinated mice is significant (p :S0.05, Mann-Whitney U test). Panel F, For KLH-SHe-vaccinated mice, hightiters of SHe-specific IgG antibodies present in the BAL fluid stronglycorrelate with reduction of RSV replication. The graphs show, for eachKLH-SHe-vaccinated mouse, the titer of SHe-specific BAL IgG antibodiesand the number of PFU/lung that could be detected five days afterinfection. In the graph, the best fitting curve and its R2 (coefficientof determination) are shown.

FIG. 19: Passive immunization with KLH-SHe immune serum reduces RSVinfection in mice. Panel A, ELISA-based determination of theSHe-specific IgG antibodies present in the sera of individual mice afterthe third immunization (boost 2) with the indicated vaccmes. Panel B,Passive immunization with KLH-SHe immune serum reduces RSV infection mmtce. Serum from KLH-SHe- or KLH-vaccinated mice or PBS wereadministrated intranasally to mice one day before and one day after RSVchallenge. Five days after challenge with 10⁶ PFU RSV, the mice of theindicated groups were sacrificed and lung homogenates were prepared todetermine the viral lung titer by plaque assay. The graph shows thenumber of plaque forming units per lung of each mouse. The detectionlimit of the plaque assay is 20 PFU per lung. The difference in RSV lungtiter between the KLH-SHe-vaccinated and the KLH-vaccinated mice issignificant (p :S 0.05, Mann-Whitney U test). Panel C, Passiveimmunization with KLH-SHe serum does not induce enhanced disease uponRSV infection. The graph shows the mean+/−SEM relative body weight ofeach mouse, calculated as the ratio between the weight at a specific dayand the weight at the day of the first passive immunization, multipliedby 100. The difference in relative body weight between the mice thatwere treated with KLH-SHe serum and the mice that were treated with KLHserum is significant (p :S 0.005, Mann-Whitney U test).

FIG. 20: Chemical linkage of SHeB peptides to the immunodominant loopsof mHBc virus-like particles. Coomassie blue stained SDS-PAGE analysisof mHBc VLPs, mHBc VLPs linked to the SMBS heterobifunctionalcrosslinker (mHBc-SMBS) and purified mHBc-SMBS VLPs with chemicallylinked SHeB peptides (mHBc-SHeB).

FIG. 21A and FIG. 21B: Binding of Serum of mHBc-SHeB-vaccinated mice tothe surface of RSV B infected cells. Vero cells were infected with a RSVB clinical isolate or mock infected. Seventy-two hours after infection,the cells were fixed and either permeabilized or not permeabilized.Infected and mock infected cells were stained with serum of amHBc-SHeB-vaccinated mouse or with serum of KLH-vaccinated mice, asindicated. Binding of mHBc-B or KLH serum antibodies to the cells wasanalyzed by using Alexa4SS linked anti-mouse IgG antibodies. FIG. 21A,For microscopic analysis, the cells were also stained with the nucleardye DAPI. FIG. 21B, For flowcytometric analysis, the non-permealizedcells were also stained with a goat anti-RSV serum to identify the RSV Binfected cells. Binding of goat anti-RSV serum antibodies to the cellswas determined by using Alexa633 linked anti-goat IgG antibodies. Thegraphs represent Alexa4SS intensity/Alexa633 intensity contour plots ofthe indicated cells.

FIG. 22: Vaccination with mHBc-SHeB induces SHeB-specific antibodies andreduces RSV B-induced pulmonary inflammation. Panel A, ELISA-baseddetermination of the SHeB- and SHeA-specific IgG antibodies present inthe pooled sera of mice after the first (im.), the second (boost 1) andthird mHBc-SHeB immunization (boost 2). Panel B, ELISA-baseddetermination of the SHe-specific IgG, IgG1 and IgG2a antibodies presentin the pooled sera of mice that were vaccinated with KLH-SHe. Panels Cand D, ELISA-based determination of SHeB- (Panel C) and SHeA-specific(Panel D) IgG antibodies present in the sera of individual mice thatwere vaccinated with the indicated vaccines. Panel E, The total numberof cells present in the BAL fluids of RSV-infected mice that had beenvaccinated with the indicated vaccines. There are significantly lesscells present in the BAL fluid of mice that had been vaccinated withmHBc-SHe compared to BAL fluid of mice that had been vaccinated withmHBc (p :S 0.05, Mann-Whitney U test). Panel F, The number of CD4+ Tcells, CDS+ T cells, monocytes, neutrophils and eosinophils present inthe BAL fluids. There are significantly less CDS+ T cells present in theBAL fluid of mice that had been vaccinated with mHBc-SHe compared to theBAL fluid of mice that had been vaccinated with mHBc (p :S 0.05,Mann-Whitney U test).

FIG. 23: Expression and purification of the LPP(s)-SHe protein. Panel A,Expression of the LPP(s)-SHe protein. pLH36-HisDEVD-LPP(s)-SHetransformed E. coli cells were either stimulated with 1 mM1-thio-B-d-galactopryanoside (IPTG) or not. Four hours later, crudeextracts were prepared by sonication followed by centrifugation(13000×g, 30 minutes, 4° C.). The supernatant was analyzed by SDS-PAGEand Western blotting using the SHe-specific 3G8 monoclonal antibody.Panel B, Analysis of purified LPP(s)-SHe protein. After purification,the LPP(s)-SHe protein was analyzed by SDS-PAGE, Coomassie blue staining(left) and Western blot (right) analysis using the SHe-specific 3G8monoclonal antibody.

FIG. 24: schedule of the vaccination of the cotton rats. Group numbersrefer to: Group 1, six Cotton rats (CR) no vaccine and challenged withRSV on day +63 (infection control); Group 2, six CR inoculatedintranasally with RSV-Tracy at 2.04×10⁵ PFU/CR on Day 0; Group 3, sixCR, each vaccinated intraperitoneally (IP) with KLH-SHe+IFA; Group 4,six CR, each vaccinated intraperitoneally (IP) with KLH+IFA (vehiclecontrol); Group 5, six CR, each vaccinated intramuscularly (IM) with1:10 formalin-inactivated (FI) RSV-Bernett grown in Vero cells (positivecontrol for immune exacerbation upon challenge).

DETAILED DESCRIPTION Examples Materials and Methods to the ExamplesCloning and Plasmid Construction

Construction of the pLT32 Flag-COMPcc-SHe expression plasmid. A plasmidcontaining the coding sequence of Flag-COMPcc-SHe (FIG. 1, Panel B) wasordered at Genscript (SEQ ID NO:31). The Flag-COMPcc-SHe coding sequencewas ligated as a Ndei/Noti fragment in a Nde1/Not1 opened pLT32Hbacterial expression vector (Mertens et al., 1995).

Construction of the pCAGGS-Etag-SH expression vector. Total RNA of RSVA2-infected Hep-2 cells was prepared using the High Pure RNA tissue kit(Roche, Mannheim) according to the manufacturer's instructions. AftereDNA synthesis, the RSV A2 SH coding sequence was amplified using thefollowing forward and reverse primers(5′ATAAGAAAGCGGCCGCTATGGAAAATACATCCATAACAATAG3′ (SEQ ID NO:36);5′GAAGATCTCTATGTGTTGACTCGAGCTCTTGGTAACTCAAA3′ (SEQ ID NO:37)). The PCRproduct was digested with Not1 and Bgl11 and ligated in a Noti/Bgl11opened pCAGGS-PTB-Etag expressiOn vector (Comelis et al., 2005). Theresulting vector pLT32-Flag-COMPcc-SHe was deposited under the Budapesttreaty at BCCM (BCCM/LMBP: Technologiepark 927, 9052 Zwijnaarde,Belgium) under deposit number LMBP 6817 on 8 Nov. 2010.

The construction of the pCAGGS-Luc expression vector was describedearlier (Schepens et al., 2005; referred as pCAGGS-HIF-RLuc).

Construction of the pLT32 mHBc expression vector. The coding sequence ofmHBc, as described earlier by Jegerlehner et al., as part of the “abl”plasmid, was ordered at Geneart (SEQ ID NO:32) (De Filette et al., 2005;Jegerlehner et al., 2002). This coding sequence was cloned as aNdei/Not1 fragment in a Ndei/Not1 opened pLT32H bacterial expressionvector.

Construction of the pLT32 SHe-tGCN4-Flag expression vector. To constructpLT32 SHe-tGCN4, the SHe coding sequence was fused to the tGCN4-Flagcoding sequence by fusion per. The SHe fragment for fusion per wasamplified using the primers: 5′GGAATTCCATATGAACAAGTTATGTGAGTACAACG3′(SEQ ID NO:38) and 5′GATTTGTTTTAAACCTCCTGTATTTACTCGTGCCCGAGGCAA3′ (SEQID NO:39) and a template plasmid that was ordered at Geneart (SEQ IDNO:33) and that contains the coding sequence of the RSV A2 SH ectodomain(NKLCEYNVFHNKTFELPRARVNT) (SEQ ID NO:40). The GCN4 fragment for fusionPCR was amplified using the primers5′CCCAAGCTTCTAACATTGAGATTCCCGAGATTGAGA3′ (SEQ ID NO:41) and5′TATTAACCCTCACTAAAGGGAAGG3′ (SEQ ID NO:42) and a template plasmid thatcontains the tGCN4 coding sequence, C-terminally fused to the codingsequence of three successive Flag-tag sequences (SEQ ID NO:34; DeFilette et al., 2008). The two PCR fragments were fused using theprimers: 5′GGAATTCCATATGAACAAGTTATGTGAGTACAACG3′ (SEQ ID NO:43) and5′TATTAACCCTCACTAAAGGGAAGG3′ (SEQ ID NO:44). This fusion PCR product wascloned as a Ndei/Hind111 fragment in a Ndei/Hind111 opened pLT32Hbacterial expression vector. The resulting pLT32 SHe-tGCN4-Flag wasdeposited under the Budapest treaty at BCCM (BCCM/LMBP: Technologiepark927, 9052 Zwijnaarde, Belgium) under deposit number LMBP 6818 on 8 Nov.2010.

The construction of the PLT32 M2e-tGCN4 expression vector was describedearlier (De Filette et al., 2008).

Construction of the pLH36-HisDEVD-LPP(5rSHe expression plasmid. Aplasmid containing the coding sequence of the LPP(s) tryptophan-zipperfused to the coding sequence of the SH ectodomain separated by thecoding sequence of a GlyGly linker was ordered at Genscript. This codingsequence was amplified using the following forward and reverse primers(5′GCGAAATGGGATCAGTGGAGCAGC-3′ (SEQ ID NO:53);5′AATATAGGATCCCTAGGTCGCCCAGTTATCCCAGCG-3′ (SEQ ID NO: 54)),phosphorylated and digested with Bamm. The pLH36-HisDEVD-LPP-SHe wasconstructed by a three-point ligation using the described PCR fragment,Bamm!Pst1-digested pLT32 plasmid fragment and EcoRV/Pst1-digested pLH36fragment. The sequence of the constructed pLH36-HisDEVD-LPP(srSHeplasmid is displayed in SEQ ID N0:49.

Expression and Purification of SHe-tGCN4, M2e-tGCN4, Flag-COMPcc-SHe,mHBc and LPP(5rSHe

A 30-ml preculture of pLT32SHe-tGCN4-transformed E. coli was grown at28° C. in Luria broth and used to inoculate 1 liter of fresh medium. Atan A600 of 0.6-0.8, the cells were treated with 1 mm isopropyl 1-thio--d-galactopyranoside, incubated for another four hours, and thencollected by centrifugation (6000×g, 20 minutes, 4° C.). The bacterialpellet was resuspended in 20 ml Tris-HCl buffer (50 mM Tris-Hcl, 50 mMNaCl and 1 mM EDTA), pH 8, and sonicated. Bacterial debris was pelletedby centrifugation (20,000×g, one hour, 4° C.). The supernatant wasapplied to a DEAE Sepharose column pre-equilibrated with Tris-HCl buffercontaining 50 mM NaCl (buffer A). After washing, the bound proteins wereeluted by a two-step gradient going from 0-40% buffer B (50 mM Tris-Hcl,1 M NaCl) and 40-100% buffer B. Fractions containing SHe-tGCN4 werepooled, adjusted to 25% ammonium sulfate saturation, and applied to aphenyl-Sepharose column pre-equilibrated with 25% ammonium sulfate, 50mm Tris-HCl, pH 8. Bound proteins were eluted with a two-step gradient.The two-step elution was performed with 0-40% and 40-100% 50 mM Tris-HClbuffer, pH 8 (buffer A). The fractions containing SHe-tGCN4 were loadedon a Superdex 75 column. Gel filtration was performed inphosphate-buffered saline (PBS), and the fractions containing SHe-tGCN4were pooled and stored at −70° C.

Expression and purification of flag-COMPcc-SHe was identical toSHe-tGCN4 apart from the use of a Q Sepharose column for anion exchangechromatography instead of a DEAE Sepharose column.

The expressiOn and purification of M2e-tGCN4 was described before (DeFilette et al., 2008).

Expression and purification of mHBc was identical to SHe-tGCN4 apartfrom the use of a Sephacryl 5400 column for gel filtrationchromatography instead of Superdex 75 column.

Expression and purification of LPPr5y-SHe. A 30-ml preculture ofpLH36-HisDEVD-LPP(s)-SHe-transformed E. coli cells was grown at 28° C.in Luria broth with ampicillin and used to inoculate 3 liters of freshmedium. At an A₆₀₀ of 0.6-0.8, the cells were treated with 1 mMisopropyl 1-thio- -d-galactopyranoside, incubated for another fourhours, and then collected by centrifugation (6000×g, 20 minutes, 4° C.).The bacterial pellet was resuspended in 300 ml buffer containing 20 mMNaH2P04/Na2HP04, 300 mM NaCl and 5 mM imidazole, pH 7.5 and sonicated.Bacterial debris was pelleted by centrifugation (20,000×g, one hour, 4°C.). The supernatant was loaded on a Nickel-Sepharose columnpre-equilibrated with buffer containing 5 mM Imidazole. After washing,the bound proteins were eluted by a step-wise (50 mM, 100 mM, 200 mM and400 mM) imidazole gradient. Fractions containing LPP(s)-SHe were pooled,desalted and further purified on a Q-sepharose column. The sample wasapplied to a DEAE Sepharose column pre-equilibrated with Tris-HCl buffercontaining 50 mM NaCl (buffer A). After washing, the bound proteins wereeluted by a two-step gradient going from 0-40% buffer B (50 mM Tris-Hcl,1 M NaCl) and 40-100% buffer. The fractions containing LPP<srSHe wereloaded on a Superdex 75 column. Gel filtration was performed inphosphate-buffered saline (PBS) and the fractions containing LPPcsJ-SHe.

Adjuvants

A detoxified mutant of heat-labile E. coli enterotoxin, LTR192G, wasused for intranasal (i.n.) administration; this preparation wasgenerously provided by Dr. J. Clements (Department of Microbiology andImmunology, Tulane University Medical Center, New Orleans, La., USA)(Norton et al., 2010).

Chemical Linking and Characterization of SHe-HBc Particles

SHe(cc4s), a chemically synthesized, HPLC-purified SHe peptide in whichthe naturally occurring cysteine was replaced by a serine and to which acysteine was added at the N-terminus was ordered at Pepscan (Pepscan,Lelystad). The SHe(cc4s) peptide was via its N-terminal cysteine residuefused to a Lysine in the immunodominant loop of mHBc on the surface ofHBc VLPs by chemical linkage using the heterobifuctional sulfo-MBS(Pierce), according to the manufacturer's instructions. In short, 400llg mHBc, dissolved in 200 lll PBS, was incubated with Sulfo-MBS (at afinal concentration of 1 mg/ml) for one hour. After removal of unboundSulfo-MBS molecules by size exclusion chromatography, sulfo-MBS-linkedmHBc VLPs were diluted in 2 ml H₂O. Subsequently, 100 lll SHe(cc4s)peptide (dissolved in 100 ml PBS) was added and incubated for one hourat room temperature to allow cross-linking of the peptide to the mHBcVLPs. Finally, free SHe(cc4s) peptide was removed by size exclusionchromatography. The purity and cross-linking efficacy was tested viaSDS-PAGE followed by Coomassie staining.

Cells

Hep-2 cells (ATCC, CCL-23), Vero cells (ATCC, CCL-81), HEK293T cells (agift from Dr. M. Hall) and A549 cells (ATCC, CCL-185) were grown in DMEMmedium supplemented with 10% heat-inactivated fetal calf serum (FCS), 1%penicillin, 1% streptomycin, 2 mM L-glutamine, non-essential amino acids(Invitrogen, Carlsbad, Calif.), and 1 mM sodium pyruvate.

Mice and Viruses

Specific pathogen-free, female BALB/c mice were obtained from CharlesRiver (Charles River Wiga, Sulzfeld, Germany). The animals were housedin a temperature-controlled environment with 12-hour light/dark cycles;food and water were delivered ad libitum. Mice were immunized at 8 weeksof age after one week adaptation in the animal room.

The animal facility operates under the Flemish Government License NumberLA1400091. All experiments were done under conditions specified by law(European Directive and Belgian Royal Decree of Nov. 14, 1993) andauthorized by the Institutional Ethical Committee on ExperimentalAnimals.

RSV A2, an A subtype of RSV (ATCC, Rockville), was propagated byinfecting monolayers of Vero cells, with 0.1 MO1 in the presence ofgrowth medium containing 1% FCS. Five to seven days after infection, thecells and growth medium were collected, pooled and clarified bycentrifugation (450×g). To concentrate the virus, the clarifiedsupernatant was incubated for four hours at 4° C. in the presence of 10%polyethylene glycol (PEG6000). After centrifugation (30 minutes at3000×g), the pellet was resuspended in Hank's balanced salt solution(HMS), containing 20% sucrose, aliquoted and stored at −80° C.

Intranasal Immunizations and Infections

For intranasal immunization or infection, the mice were slightlyanesthetized by isofluorane. The final volume used for administration ofvaccine+adjuvant or virus was 50-tl (25-tl per nostril).Vaccines+adjuvant were formulated in PBS, whereas the viral inoculum wasformulated in HBSS.

Determination of Lung Viral Titer by Plaque Assay

Three or four days post-challenge, the mice were sacrificed. The mouselungs were removed aseptically and homogenized with a Heidolph RZR 2020homogenizer for 30 seconds in 1 ml HMS containing 10% sucrose. Lunghomogenates were subsequently cleared by centrifugation at 4° C. andused for virus titration on Hep-2 cells. Monolayers of Hep-2 cells wereinfected with 50-tl of serial 1:3 dilutions of the lung homogenates in a96-well plate in serum-free OPTI-MEM® medium (Invitrogen) supplementedwith penicillin and streptomycin. Four hours later, the cells werewashed twice with DMEM medium containing 2% FCS and incubated for fivedays at 37° C. in 50-tl overlay medium (completed DMEM medium containingI % FCS, 0.5% agarose). The cells were fixed by adding 50-tl of a 4%paraformaldehyde solution on top of the agarose overlay. After overnightfixation at 4° C., the overlay medium and paraformaldehyde solution wereremoved, the cells were washed twice with PBS and blocked with PBScontaining 1% BSA (PBS/BSA). Subsequently, polyclonal goat anti-RSVserum (AB1128, Chemicon International) was added ( 1/4000). Afterwashing three times with PBS/BSA, the cells were incubated withhrp-conjugated anti-goat IgG antibodies (SC2020, Santa Cruz) for 30minutes. Non-binding antibodies were removed by washing four times withPBS/BSA containing 0.01% TRITON® X-100 and once with PBS. Finally, theplaques were visualized by the use of TrueBlue peroxidase substrate(KPL, Gaithersburg). The plaques of different dilutions were countedand, for each dilution, the number of PFU per lung (1 ml) was calculatedas: number of plaques present in the dilution×the dilution×20 (=1000 Jlltotal supernatant volume/50 Jll of the volume of supernatant used toinfect the first well of the dilution series). The number of PFU/lungwas then calculated as the average number of PFU/lung calculated for thedifferent dilutions. As each supernatant of the homogenized lungs wastested in duplicate, the final number of PFU/lung was calculated as theaverage of these duplicates.

Determination of Lung Viral Titer by qRT-PCR

To determine the lung RSV load by qRT-PCR, lung homogenates wereprepared and clarified as described above. Total RNA from these lunghomogenates was prepared by the use of the High Pure RNA tissue kit(Roche, Mannheim) according to the manufacturer's instructions. eDNA wasprepared by the use of hexamer primers and the Transcriptor First StrandeDNA synthesis kit (Roche, Mannheim). The relative levels of genomic RSVM eDNA were determined by the use of qRT-PCR using primers specific forthe genomic RNA of the RSV A2 M-gene (5′TCACGAAGGCTCCACATACA3′ (SEQ IDNO:45) and 5′GCAGGGTCATCGTCTTTTTC3′ (SEQ ID NO:46)) and a nucleotideprobe (#150 Universal Probe Library, Roche) labeled with fluorescein(FAM) at the 5′-end and with a dark quencher dye near the -3′ end. Therelative amount of GADPH mRNA was determined by qRT-PCR using primersspecific for mouse GADPH (5′TGAAGCAGGCATCTGAGGG3′ (SEQ ID NO:47) and5′CGAAGGTGGAAGAGTGGGAG3′ (SEQ ID NO:48) and LIGHTCYCLER® 480 SYBR® GreenI Master Mix (Roche). The relative amount of genomic RSV RNA per lunghomogenate was calculated as the ratio between the relative amount ofRSV M-gene RNA and the relative amount of mouse GADPH mRNA.

Peptide ELISA

Two weeks after each immunization, blood samples were collected from thelateral tail vein. The final bleeding was performed by cardiac punctureof animals anesthetized with avertin. Blood was allowed to clot for 30minutes at 37° C., and serum was obtained by taking the supernatant fromtwo subsequent centrifugations.

Serum antibody titers were determined by ELISA using pooled sera fromthe group. To determine M2e or SHe-specific antibody titers, microtiterplates (type II F96 MaxiSorp, Nunc) were coated with, respectively,50)ll of a 2) lg/ml M2e-peptide solution or 2) lg/ml SHe-peptidesolution in 50 mM sodium bicarbonate buffer, pH 9.7, and incubatedovernight at 37° C. After washing, the plates were blocked for one hourwith 200)ll of 1% BSA in PBS. After a one-hour incubation, the plateswere washed again. A series of ⅓ dilutions of the different serumsamples, starting with a 1/100 dilution, were loaded on thepeptide-coated plates. The bound antibodies were detected with aperoxidase-labeled antibody directed against mouse isotypes IgG1 orIgG2a (Southern Biotechnology Associates, Inc., Birmingham, Ala., USA)and diluted 1/6000 in PBS+1% BSA+0.05% TWEEN® 20. After washing, themicrotiter plates were incubated for five minutes with TMB substrate(Tetramethylbenzidine, Sigma-Aldrich). The reaction was stopped byaddition of an equal volume 1 M H3P04 and the absorbance at 450 nm wasmeasured. Endpoint titers are defined as the highest dilution producingan O.D. value twice that of background (pre-immune serum).

Flow Cytometric Analysis

Hek293T cells were transfected with the indicated expressiOn vectors.Twenty-four hours later, the cells were detached using enzyme-freedissociation buffer (Invitrogen, Carslbad, Calif.), washed once with PBSand incubated for one hour in PBS containing 1% BSA (PBS/BSA).Subsequently, the cells were incubated with the indicated serum orantibodies at the indicated concentrations. One hour later, the cellswere washed three times with PBS/BSA and incubated with the anti-mouseIgG alexa 633 secondary antibodies for 30 minutes. After washing thecells four times with PBS/BSA and once with PBS, the cells were analyzedusing a Becton Dickinson LSR II flow cytometer. Single GFP-expressingcells were selected based on the peak surface of the sideward scattersignal, the peak surface and peak height of the forward scatter signaland the peak surface of the green fluorescence signal. Finally, of theseGFP-positive single cells, the alexa 633 fluorescence signal wasmeasured.

Immunostaining

Vero cells were either mock infected or infected with 0.5 MO1 of RSV A2in the presence of serum-free medium. Four hours later, the free viruswas washed away and the cells were incubated in growth medium containing1% FCS. Sixteen hours later, the cells were washed once with PBS andfixed with 2% paraformaldehyde for 20 minutes. Subsequently, the cellswere washed twice with PBS and permeabilized with 0.2% TRITON® X-100detergent for five minutes. After washing once with PBS, the cells wereblocked in PBS/BSA. One hour later, SHe-specific 3G8 monoclonal antibodyor isotype control antibody was added at a final concentration of 5flg/ml. After washing the cells twice with PBS/BSA, polyclonal anti-RSVgoat serum was added. One hour later, the cells were washed three timeswith PBS/BSA. The binding of the indicated antibodies to the cells wasanalyzed by the use of anti-mouse and anti-goat IgG antibodies labeledwith, respectively, alexa 488 and alexa 568 fluorescent dyes. Confocalimages of the stained cells were recorded with a Zeiss confocalmicroscope.

Generation of SHe mAb Producing Hybridomas

Stable hybridomas cells producing SHe-specific monoclonal antibodies(mAb) were generated by hybridoma technology (Kohler and Milstein 1975).Briefly, SHe-specific hybridomas were derived from individual mice thatwere immunized i.p. three times at three-week intervals with 10 fig ofSHe-tGCN4 vaccine adjuvanted with ALHYDROGEL® (Brenntag Biosector).Three days before fusion, mice were boosted an additional time with thesame formulation and splenocytes were isolated then fused to SP2/0-Ag14myeloma cells in the presence of PEG 1500 (Roche Diagnostics GmbH,Germany). Fused cells were grown in RPMI 1640 medium supplemented with10% Fetal bovine serum, 10% BM Condimed Hl (Roche Diagnostics GmbH,Germany), 2 mM L-glutamine, and 24 f.lM beta-mercaptoethanol and 1×HATsupplement (Invitrogen, Carlsbad, Calif.). Hybrids secretingSHe-specific antibodies were identified by SHe peptide ELISA screeningand monoclonal antibodies producing hybrids were obtained after tworounds of sub-cloning by limiting dilution procedure. Monoclonalantibodies were purified on a protein A-Sepharose column (electricalengineering biosciences).

The resulting hybridomas were deposited under the Budapest treaty atBCCM (BCCM/LMBP: Technologiepark 927, 9052 Zwijnaarde, Belgium) underdeposit numbers LMBP 7795CB for 3G8 on 8 Nov. 2010 and LMBP 7796CB for3D11 on 10 Nov. 2010, respectively.

Example 1: Design, Expression and Purification of Flag-COMPcc-SHe

The SH protein is expressed at the surface of RSV virions and the plasmamembrane of RSV-infected cells as a pentamer. The pentamericorganization of SH is organized by the SH transmembrane domain, whicholigomerizes as a coiled coil of five parallel alpha-helices. In orderto present the C-terminal SH ectodomain (SHe) of RSV A as a pentamerthat mimics its natural conformation, SHe was genetically fused to theshort pentameric coiled coil domain of the rat cartilage oligomericmatrix protein (COMPcc), which is also composed of five parallelalpha-helices (Malashkevich et al., 1996; FIG. 1). A Flag-tag was fusedto the N-terminus of COMP, rendering Flag-COMPcc-SHe. Flag-COMPcc-SHewas cloned in a pLT-32 (Mertens et al., 1995) expression vector,expressed in E. coli and purified. Gel filtration analysis revealed thatFlag-COMPcc-SHe eluted as a 55-60 kDa complex, indicating that the 11kDa Flag-COMPcc-SHe proteins do indeed oligomerize into pentamers (FIG.2).

Example 2: Flag-COMPcc-SHe Vaccination Induces SHe-Specific Antibodiesand Protection Against RSV Infections

To test if vaccination with Flag-COMPcc-SHe could evoke protectionagainst RSV infection, we used a BALB/c mouse RSV infection model.BALB/c mice were immunized three times intranasally with 25 llg ofFlag-COMPcc-SHe in combination with 1 llg E. coli heat-labileenterotoxin LTR192G adjuvant. PBS and the Influenza A M2 ectodomainfused to a tetrameric GNC4 scaffold (M2e-tGNC4) (De Filette et al.,2008) were used as negative controls. Immunizations were performed everyfortnight. A single RSV infection (5×10⁵ PFU) was used as positivecontrol. Between the first and the second week after each immunization,blood was collected to investigate the induction of SHe-specific IgGantibodies. The presence of SHe-specific antibodies was first tested bySHe peptide ELISA. M2e peptide ELISA was used as negative control. FIG.3 demonstrates that SHe peptide-specific IgG antibodies are induced andboosted after, respectively, the second and third immunization withFlag-COMPcc-SHe. Three successive Flag-COMPcc-SHe/LTR192G immunizationsresulted in high levels of IgG2a SHe-specific antibodies but only lowlevels of IgG1 SHe-specific antibodies, indicating a Th1-oriented/drivenimmune response. No SHe-specific IgG antibodies could be detected in PBSor M2e-tGCN4/LTR192G vaccinated mice (FIG. 3, Panels A, Band C). Asexpected, no M2e-specific antibodies could be detected in the sera ofFlag-COMPcc-SHe/LTR192G or PBS vaccinated mice data. Mice that wereimmunized with M2e-tGCN4 accumulated a high titer of M2e-specific IgG2aantibodies, in accordance with previous results (De Filette et al.,2008).

Next, we investigated if SHe-specific antibodies present m theFlag-COMPcc-SHe immune serum could bind to cells expressing the RSV-SHprotein at their surface by flow cytometry. HEK-293T cells weretransfected with a GFP expression vector, in combination with either aSHexpression vector (pCAGGS-Etag-SH) or a Luciferase expression vector(pCAGGS-Luc) as negative control. Twenty-four hours after transfection,the cells were detached, stained with different dilutions ofFlag-COMPcc-SHe or M2e-tGCN4 immune serum and analyzed by flowcytometry. FIG. 4 illustrates that, in contrast to M2e-tGCN4 immuneserum, serum from Flag-COMPcc-SHe-vaccinated mice specifically binds SHprotein expressed at the surface of living cells.

To test if Flag-COMPcc-SHe/LTR192G vaccination can elicit protectionagainst RSV infection, the mice were challenged with 1×10⁶ PFU RSV A2nine weeks after the last immunization. Four days after infection, themice were sacrificed to determine the viral lung titer by plaque assay.FIG. 5 illustrates that compared to PBS- and M2e-tGCN4-vaccinated mice,vaccination with Flag-COMPcc-SHe lowered RSV replication. No virus wasdetected in the mouse that was infected with living RSV beforechallenge.

Vaccination with formalin-inactivated virus or the RSV G protein caninduce enhancement of disease upon infection, resulting in significantmorbidity, by the induction of an unbalanced Th2 immune response (Princeet al., 1986). To test if Flag-COMPcc-SHe vaccination might also induceenhancement of disease, we monitored the body weight before and afterRSV challenge (FIG. 6). No weight loss was observed in any of the mousegroups after RSV challenge. This strongly suggests that Flag-COMPcc-SHevaccination does not result in enhancement of disease upon RSVinfection.

Example 3: Design, Construction and Purification of mHBc-SHe

The Hepatitis B virus core protein (HBc) virus-like particle (VLP) canpresent antigens as a dense array. In this way, HBc-VLPs can induce astrong humoral immune response toward the presented antigen (Boisgeraultet al., 2002). Therefore, as an alternative to presenting SHe as apentamer, the SH ectodomain was presented in the immunodominant regionloop of mHBc-VLPs. HBc-SHe-VLPs were obtained by chemical linkage of SHepeptides to mHBc, a mutant of HBc in which a lysine was introduced inthe top of the HBc immunodominant region (De Filette et al., 2005). Toenable chemical linking, a cysteine residue was added to the N-terminusof SHe. In addition, the cysteine residue, present at position 4 of theSHe peptide, was replaced by a serine residue. This peptide was calledSHe-CC4S. After purification of the mHBc-SHe-VLPs, by size exclusionchromatography, the degree of cross-linking was examined by SDS PAGE.FIG. 7 illustrates that approximately 50% of the HBc proteins ischemically linked to a SHe-CC4S peptide. The slower migrating bandslikely represent mHBc monomers to which two or three SHe(cc4s) peptideswere linked. To test if SHeCC4S-linked mHBc proteins still assemble intoVLPs of the expected size (30-34 nm), Dynamic Light Scattering analyseswas performed on the generated mHBc-SHe particles and the 1604 M2e-HBcVLP as fully functional reference. FIG. 8 illustrates that the sizedistribution of mHBc-SHe-CC4S overlaps with that of the 1604 M2e-HBccontrol, with a maximum at 30 nm, which corresponds with the reportedsize of HBc VLPs (Clarke et al., 1987).

Example 4: Design, Construction and Purification of SHe-tGCN4-Flag

Next to presenting the SHe peptide at the surface of mHBc VLPs, SHe wasalso fused to tGCN4, which is known to induce a strong humoral responsetoward fused peptides (Ref marina GCN4). SHe and a Flag-tag weregenetically linked to, respectively, the 5′-end and the -3′ end of thetGCN4 coding sequence and cloned into a PLT32 expression vector. Afterexpression in E. coli, recombinant SHe-tGCN4-Flag was purified by anionexchange, hydrophobic interaction and gel filtration chromatography(FIG. 9).

Example 5: mHBc-SHe(CC4S) and SHe-tGCN4 Vaccination Induces SHe-SpecificAntibodies and Protection Against RSV Infections

To test if vaccination with mHBc-SHe(CC4S) and SHe-tGCN4 can evokeprotection against RSV infections, Balb/c mice were vaccinated threetimes intranasally with 10 llg mHBc-SHe(CC4S) and SHe-tGCN4 incombination with 1 llg LTR192G adjuvant. PBS and empty mHBc, the latterin combination with 1 llg LTR192G, were used as negative controls.Immunizations were performed every three weeks. A single RSV infection(5×10⁵ PFU) was used as positive control. Between the second and thethird week after each immunization, blood was collected to investigatethe induction of SHe-specific IgG antibodies. The presence ofSHe-specific antibodies was tested by SHe peptide ELISA. FIG. 10, PanelA, demonstrates that SHe peptide-specific IgG antibodies are induced andboosted after, respectively, the second and third immunization withmHBc-SHe(CC4S) and SHe-tGCN4. Three successive Flag-COMPcc-SHe/LTR192Gimmunizations resulted in high levels of IgG2a SHe-specific antibodiesand somewhat lower levels of IgG1 SHe-specific antibodies, indicating aTh1-oriented/driven immune response (FIG. 10, Panel B).

To test if vaccination with mHBc-SHe(CC4S) or SHe-tGCN4 can hamper RSVinfection, the mice were challenged with 5×10⁶ PFU RSV A2 three weeksafter the last boost immunization. Three days after challenge, the micewere sacrificed to determine the pulmonary RSV A2 levels by QPCR. FIG.11 shows that all mice that were vaccinated with mHBc-SHe(CC4S) orSHe-tGCN4 or mice that were infected beforehand with RSV, have lowerpulmonary levels of genomic RSV RNA than mice that were vaccinated withmHBc. These data confirm our previous observation that mucosal SHe-basedvaccination can partially protect mice against RSV replication.Remarkably, all mice that were vaccinated with an empty mHBc incombination with the LTR192G adjuvant, displayed lower levels of RSVthan mice that were immunized with PBS without LTR192G adjuvant. Thismight be explained by the effect of LTR192G on the mouse innate immunesystem. The E. coli heat labile entertoxin has been shown to providegeneric protection against lung viral infections, including RSV, viainnate imprinting (ref Williams and Hussel 2004). The effect of innateimprinting by LTR192G on lung viral replication appears to be transientas the impact of TLR192R on RSV replication is strongly reduced whenviral infection occurs nine weeks after the last LTR192G administration.Again, none of the mice showed significant body weight loss, indicatingthat vaccination with SHe when presented by VLPs or tGCN4 is notinducing enhancement of disease upon challenge (FIG. 12).

Example 6: Production and Testing of SHe-Specific Monoclonal Antibodies

To investigate if SHe-specific antibodies that can interact withinfected cells can provide protection against RSV infections, wedeveloped RSV SHe-specific monoclonal antibodies based on SHe-TGCN4immunized mice. One IgG1 (3D11) and one IgG2a (3G8) subtype hybridomathat produced antibodies that efficiently bound to SHe peptide in anELISA were selected, subcloned and used for antibody production. The3D11 and 3G8 were purified via protein A affinity chromatography andtested for binding efficacy to SHe via an ELISA. FIG. 13 shows that 3D11and 3G8 can bind to coated SHe peptide and are, respectively, of theIgG1 and IgG2a subtype.

As antibodies can protect against viral infections via recognition andkilling of infected cells by (ADCC) or CDC, we investigated if theSHe-specific mAbs 3D11 and 3G8 can recognize SH at the surface of cells.Therefore, Hek293T cells were transfected with an RSV SH expressionvector or with a control Firefly luciferase vector (Schepens et al.,2005), both in combination with a GFP expression vector. Twenty-fourhours after transfection, live cells were stained with differentconcentrations of the SHe-specific monoclonal antibodies (3D11 and 3G8)or isotype matched Influenza M2e-specific antibodies (14C2 IgG1 and aIG2a M2e-specific mAb). Polyclonal serum from Flag-COMPcc-SHe-immunizedmice was used as positive control. FIG. 14 demonstrates thatFlag-COMPcc-SHe polyclonal serum, along with both 3D11 and 3G8 mAbs, canreadily bind to SH-expressing cells but not to control cells. Incontrast, the IgG1 and IgG2a Influenza M2e-specific antibodies could notbind to SH-expressing cells. These data clearly demonstrate that both3D11 and 3G8 can recognize the ectodomain of SH expressed at the surfaceof cells.

During infection, the RSV SH protein is mainly expressed at the ER,golgi and cell membrane. In order to more directly investigate whetherthe RSV SH-specific antibodies can recognize infected cells via SHexpressed at the surface of these cells, we performed immunostaining ofRSV-infected and mock-infected cells. Human A594 lung epithelial cellswere either infected with 0.05 MO1 of RSV or mock infected. Twenty-fourhours after infection, the cells were fixed and stained with theSHe-specific mAbs 3D11 or 3G8 in combination with polyclonal anti-RSVimmune serum. FIG. 15 illustrates that the SHe-specific mABs 3D11 and3G8 can readily recognize SH at the cell membrane and near the nucleus(likely corresponding to ER and Golgi) of infected cells. This indicatesthat SHe mAbs protect against RSV infection by recognizing RSV-infectedcells. In this way, the herein-described SHe mAbs 3D11 and 3G8 can beused as prophylactic or therapeutic treatment.

Example 7: Passive Immunization Using SHe-Specific mAB 3G8 Reduces RSVReplication

To test if SHe-specific antibodies can reduce RSV replication in vivo,mice were passively immunized with SHe-specific monoclonal antibodies.SHe-specific 3G8 monoclonal antibodies, isotype control antibodies orPBS were intranasally administered to mice one day before and one dayafter RSV Challenge. Three days after RSV challenge, blood was collectedto test for the presence of mAbs in the serum of the treated mice. Fourdays after RSV challenge, the mice were sacrificed to determine theviral titer in the lungs. Peptide ELISA demonstrated the presence of lowconcentrations of SHe-specific and isotype control antibodies in theserum of mice treated with the respective antibodies (data not shown).FIG. 16 illustrates that mice that received SHe-specific monoclonalantibodies have reduced lung RSV titers as compared with mice that weretreated with PBS or isotype control monoclonal antibodies. These datasuggest that intranasal administration of SHe-specific antibodies canreduce RSV infection mmlce.

Example 8: Construction of SHe-KLH

To test if SHe-based vaccines can also protect against RSV infectionswhen this vaccine is administered via an alternative route with analternative adjuvant and with a different carrier, the vaccine wastested intraperitoneally, with keyhole limpet hemocyanin (KLH) as acamer. Maleimide-activated KLH (Pierce) was chemically linked to thepeptide

(SEQ ID NO: 50) (CGGGSNKLSEYNVFHNKTFELPRARVNT;the sequence corresponding to the RSV A SH ectodomain (SHe) isunderlined) corresponding to the RSV A SH ectodomain. To promotedirectional chemical linking, a CysGlyGlyGlySer (SEQ ID NO:55) linkerwas added to the N-terminus of the RSV A SHe peptide. In addition, thecysteine residue present in the natural RSV A SHe was substituted by aserine residue. Chemical linkage was performed according to themanufacturer's instructions (Pierce). Cross-linked KLH-SHe proteins wereisolated by size exclusion chromatography.

Example 9: Intraperitoneal Vaccination with KLH-SHe Reduces RSVReplication in Mice

To test if intraperitoneal (LP.) vaccination with a SHe-based vaccinecan evoke protection against RSV infections, Balb/c mice (six mice pergroup) were vaccinated three times intraperitoneally with 20)Ig ofKLH-SHe or KLH, each in combination with 50)ll of Freund's IncompleteAdjuvant (Millipore). PBS vaccination without adjuvant was used as anadditional negative control. Between the second and third week aftervaccination, blood was collected to determine the induction ofSHe-specific IgG antibodies. The presence of SHe-specific antibodies wasdetermined and quantified by SHe peptide ELISA. FIG. 17 (Panels A and B)demonstrate that three successive vaccinations with KLH-SHe induces highlevels of SHe-specific IgG antibodies of both the IgG1 and IgG2asubtype. No SHe-specific IgG antibodies could be detected in sera fromPBS- or KLH-vaccinated mice. In addition, flow cytometric analysisrevealed that serum derived from mice that had been vaccinatedintraperitoneally with KLH-SHe can specifically bind to HEK293T cellsthat express the RSV SH protein at their surface, whereas pre-immuneserum did not.

To test whether intraperitoneal KLH-SHe vaccination can reduce RSVinfection, the vaccinated mice were infected with 1×10⁶ PFU of RSV A2four weeks after the last vaccination. Five days after challenge, themice were sacrificed to determine the pulmonary RSV A2 titer by plaqueassay. FIG. 17, Panel D, illustrates that significantly less virus couldbe detected in the lungs of SHe-KLH-vaccinated than in the lungs ofKLH-vaccinated mice (P>0.005, Mann-Whitney U test). The observation thatamong KLH-SHe-vaccinated mice, higher titers of serum SHe-specific IgGantibodies strongly correlated (R²=0.95) with lower levels of pulmonaryRSV at day 5 post-infection, suggests that reduction of RSV replicationby KLH-SHe vaccination is mediated by SHe-specific antibodies (FIG. 17,Panel E). The body weight of all mice was monitored at the day ofinfection and the day of sacrifice. FIG. 17, Panel C, illustrates thatmice that were vaccinated with KLH-SHe gained significantly more weightthan mice that were vaccinated with KLH (P>0.005, Mann-Whitney U test).These data demonstrate that intraperitoneal vaccination with a SHe-basedvaccine can reduce RSV replication without inducing morbidity. Inaddition, these data illustrate that next to mHBc, tGCN4 and COMPcc, KLHcan also be used as a protein carrier for SHe peptide-based vaccines.Moreover, these data illustrate that next to TITERMAX®, also Freunds'Incomplete Adjuvant can also be used as an appropriate adjuvant toinduce SHe-specific immunity.

Example 10: Intranasal Vaccination with KLH-SHe Reduces RSV Replicationin Mice

To test if intranasal vaccination with KLH-SHe can evoke protectionagainst RSV infections, Balb/c mice (six mice per group) were vaccinatedthree times intranasally with 20 J/g of KLH-SHe or KLH, each incombination with 1 llg of LTR192G adjuvant. PBS vaccination withoutadjuvant was used as an additional negative control. Between the secondand third week after vaccination, blood was collected to investigate theinduction of SHe-specific IgG antibodies. The presence of SHe-specificantibodies was tested by SHe peptide ELISA. FIG. 18 (Panels A and B)demonstrate that three successive vaccinations with KLH-SHe induceSHe-specific IgG antibodies of both the IgG1 and IgG2a subtype. NoSHe-specific IgG antibodies could be detected in sera from PBS- orKLH-vaccinated mice. In addition, flow cytometric analysis revealed thatserum derived from mice that were vaccinated intranasally with KLH-SHeserum, but not pre-immune serum, can specifically bind to HEK293T cellsthat express the RSV SH protein at their surface.

To test whether intraperitoneal KLH-SHe vaccination can reduce RSVinfection, the vaccinated mice were infected with 1×10⁶ PFU of RSV A2nine weeks after the last vaccination. Five days after challenge, themice were sacrificed to collect BAL (Broncho Alveolar Lavage) fluid (3ml). The RSV A2 titer in the collected BAL fluids was determined byplaque assay. FIG. 18, Panel E, illustrates that significantly lessvirus could be detected in the lungs of KLH-SHe-vaccinated mice than inthe lungs of KLH-vaccinated mice (P>0.05, Mann-Whitney U test). Thepresence of SHe-specific IgA and IgG antibodies in the collected BALfluids was analyzed by SHe peptide ELISA. This analysis revealed that incontrast to PBS- and KLH-vaccinated mice, the BAL fluids of micevaccinated with KLH-SHe contained both IgG and IgA SHe-specificantibodies (FIG. 18, Panels C and D). The levels of lgG SHe-specificantibodies present in the BAL fluid of KLH-SHe-vaccinated micecorrelated with the levels of IgG SHe-specific antibodies in the serumof the respective mice. The observation that among KLH-SHe-vaccinatedmice, higher titers of SHe-specific IgG antibodies present in the BALfluid strongly correlate (R²=0.97) with lower levels of pulmonary RSVtiters on day 5 post-infection, suggests that reduction of RSVreplication by KLH-SHe vaccination is mediated by SHe-specificantibodies (FIG. 18, Panel F). These data demonstrate that intranasalvaccination with a SHe-based vaccine can reduce RSV replication withoutinducing morbidity. In addition, these data confirm that next to mHBc,tGCN4 and COMPcc, KLH can also be used as a protein carrier for SHepeptide-based vaccines.

Example 11: Passive Transfer of KLH-SHe Immune Serum Protects AgainstRSV Infection in Mice

To further investigate if the reduction in RSV replication in mice thathave been vaccinated with a SHe-based vaccine can be mediated by RSVSHe-specific antibodies, passive transfer experiments were performed.Balb/c mice were vaccinated intraperitoneally with 20 f.lg of eitherKLH-SHe or KLH, both in combination with 75 f.ll of Freund's IncompleteAdjuvant. As an additional negative control, mice were vaccinated withPBS without adjuvant. SHe peptide ELISA illustrated that the sera of allmice that had been vaccinated with KLH-SHe contains high levels ofSHe-specific IgG antibodies. After final bleeding, the sera of the miceof each group were pooled and heat inactivated at 56° C. for 30 minutes.To test if KLH-SHe sera can protect against RSV infections, 40 f.ll ofKLH or KLH-SHe sera were administered to mice intranasally one daybefore (day −1) and one day after (day 1) RSV challenge (2×10⁵ PFU) (day0). Mice that were treated with PBS were included as additionalcontrols. The weight of all mice was monitored daily (FIG. 19, Panel C).Five days post-infection, the mice were sacrificed to prepare lunghomogenates. Plaque assay analysis demonstrated that the lunghomogenates of mice that had been treated with KLH-SHe serum containedabout 40 times less (ratio of means of viral titers) replicating virusthan the lung homogenates originating from mice treated with KLH serum(FIG. 19, Panel B). The observation that the pulmonary RSV titer of micethat were treated with KLH serum did not differ from the pulmonary RSVtiter of mice that were treated with PBS, illustrates thatadministration of control serum does not impact pulmonary RSVreplication in mice.

Example 12: Construction of mHBc-SHeB

Although highly conserved within their subtype, the SHe amino acidsequences of RSV B viruses differs from that of the RSV A subtypeviruses. Therefore, to protect against RSV B viruses, a SHe-basedvaccine most likely needs to include the RSV B SHe amino acid sequence.

A RSV B SHe vaccine was constructed by chemically linking the consensusRSV B SHe peptide (SHeB: CGGGSNKLSEHKTFSNKTLEQGQMYQINT (SEQ ID NO:51) tothe mHBc virus-like particles. To promote chemical linking, aCysGlyGlyGlySer (SEQ ID NO:55) linker was added to the N-terminus of theRSV B SHe peptide. In addition, the cysteine residue present in thenatural RSV B SHe was substituted by a serine residue. The immunogenresulting from chemical linkage of the RSV B SHe peptide to mHBc wasnamed mHBc-SHeB. After purification of the mHBc-SHeB VLPs by sizeexclusion chromatography, the degree of cross-linking was analyzed bySDS-PAGE gel electrophoresis and Coomassie staining. FIG. 20 illustratesthat more than half of the HBc monomers are cross-linked to at least oneSHe peptide.

Example 13: Immunization of Mice with mHBc-SHeB Induces SHeB-SpecificAbs that Bind to the Surface of RSV B-Infected Cells

To test whether mHBc-SHeB VLPs were immunogenic, one BALB/c mouse wasimmunized three times subcutaneously with 20 μg of mHBc-SHeB combinedwith 50 !-!1 TITERMAX® (Sigma). The three immunizations were performedwith two-week intervals. Bleedings were performed one day before eachimmunization and two weeks after the final immunization. To test whethermHBc-SHeB immune serum can recognize RSV B SH proteins expressed on thesurface of infected cells, Vero cells were either mock infected orinfected with a clinical isolate of RSV B virus (kindly provided by Dr.Marc van Ranst, University of Leuven, Leuven, Belgium). Seventy-twohours after infection, the cells were fixed and either permeabilizedusing 0.2% TRITON® X-100 or not permeabilized. The cells were thenstained with either mHBc-SHeB immune serum ( 1/100 dilution) or controlimmune serum ( 1/100 dilution) derived from BALB/c mice that had beenvaccinated with KLH (KLH serum) in combination with Freund's IncompleteAdjuvant. The samples were analyzed by immunofluorescent microscopy orflow cytometry. FIG. 21, Panels A and B, illustrate that mHBc-SHeBimmune serum can bind to both permeabilized and non-permeabilized RSVB-infected cells but not to non-infected cells. In contrast, controlimmune serum did not bind to RSV B-infected cells. This demonstratesthat vaccination of mice with mHBc-SHeB induces serum antibodies thatcan recognize RSV B-infected cells, most likely by binding to the RSV BSH protein that is expressed at the surface of RSV B-infected cells.

Example 14: mHBc-SHeB Immunization Reduces RSV Replication in Mice

To test whether mHBc-SHeB vaccination can protect mice from RSV Binfection, two groups of six mice were immunized with mHBc or mHBc-SHeBVLPs, adjuvanted with 50 l-ll of Freund's Incomplete Adjuvant. Asadditional controls, six mice were vaccinated with PBS. Vaccinationswere performed intraperitoneally, three times with three-week intervals.Bleedings were performed two weeks after each immunization. Theinduction of SHe-specific antibodies was determined by peptide ELISAusing SHeA or SHeB as coating peptides. This analysis demonstrated thatin all mice, three successive mHBc-SHeB immunizations induced hightiters of RSV B SHe-specific IgG antibodies of both IgG1 and IgG2asubtype (FIG. 22, Panels A-C). mHBc-SHeB immune serum also bound to theSHeA peptide but to a much lower extent (FIG. 22, Panels A, Band D).

Previous experiments in our and other laboratories have illustrated thatno or very little replicating virus can be rescued from RSV B-infectedmice. Nevertheless, we could observe that infections with clinical RSV Bisolates induce pulmonary inflammation and weight loss in BALB/c mice(data not shown). Therefore, we tested whether mHBc-SHeB vaccinationcould protect mice from RSV B-induced pulmonary inflammation. Six daysafter intranasal challenge of mice with 2×10⁶ PFU of an RSV B clinicalisolate, Broncho Alveolar Lavage (BAL) was performed. Mock-infected micewere used as negative control for analysis of BAL cell infiltration. TheBAL fluid was analyzed for immune cell infiltration by flow cytometry asdescribed in Bogaert et al., 2011. FIG. 22, Panels E and F, show thatRSV B infection results in pulmonary infiltration of immune cells,especially CD8+T lymphocytes, which are known to be responsible forRSV-induced morbidity in mice. However, compared to PBS- ormHBc-vaccinated mice, mHBc-SHeB-vaccinated mice displayed significantlylower pulmonary cell infiltration. These data demonstrate that mHBc-SHeBvaccination reduces RSV-related immune pathology.

Example 15: Design, Expression and Purification of the LPP(s)-SHeProtein

As an alternative protein scaffold to present SHe as a pentamer, we usedthe pentameric tryptophan-zipper described by Liu et.al. (LPP(s)), whichis derived from the E. coli LPP-56 lipoprotein (Liu et al., 2004). Thecoding sequence of the LPP(s) tryptophan-zipper was genetically fused tothe SHe coding sequence and cloned into an E. coli expression vector(pLH36) containing a hexahistidine peptide and a caspase cleavage siteas described by Mertens et al., 1995. This expression plasmid was namedpLH36-HisDEVD-LPP-SHe (SEQ ID NO:49). Expression from this plasmidrenders the chimeric LPP(s)-SHe protein (SEQ ID NO:52)(MHHHHHHPGGSDEVDAKWDQWSSDWQTWNAKWDQWSNDWNAWRSDWQAWK

(SEQ ID NO:52), His-tag sequence is underlined, linkers are in italic,DEVD caspase cleavage site is in italic+underlined, pentameric LPPtryptophan-zipper is in bold and the RSV A SH ectodomain is inbold+italic). After induction of expression in E. coli, the LPP(₅)-SHeprotein was purified by subsequent Nickel affinity, anion-exchange andgel filtration chromatography. FIG. 23 demonstrates that the LPP(s)-SHeprotein can be recognized by SHe-specific 3G8 monoclonal antibodies,both in a crude cell extract (FIG. 23, Panel A) and as a purifiedprotein (FIG. 23, Panel B).

Example 16: Cotton Rat Immunization

In order to prove the efficacy of the vaccine in an independent animalmodel, cotton rats are used. Cotton rats (Sigmondon hispidus) aresusceptible to RSV infection (Prince et al., 1978). Five groups of sixcotton rats each are used. Two groups of animals are immunizedintraperitoneally (i.p.) with 100 j.lg of KLH (vehicle control) or 100j.lg of KLH-SHe (i.e., a chemical conjugate of SHe peptide derived fromRSV-A with KLH as a carrier). KLH and KLH-SHe vaccine antigens areformulated with Freund's Incomplete Adjuvant and used to immunize cottonrats on days 0, 21, and 42. A third group of animals is immunizedintramuscularly with formalin-inactivated RSV (FI-RSV) in the presenceof alum adjuvant. The latter group serves as a positive control for theinduction of vaccine-enhanced disease that becomes apparent uponsubsequent challenge with RSV. A fourth group is infected with 2.04×10⁵plaque forming units per cotton rat of RSV-Tracy on day 0 and serves aspositive control for protection against subsequent challenge. A fifthgroup of cotton rats remains untreated until the day of challenge andserved as control for the challenge with RSV. The schedule of thevaccination is shown in FIG. 24.

Sera are collected before each immunization and on the day of challenge.On day 63, cotton rats are challenged intranasally with 2.04×10⁵ plaqueforming units of RSV-Tracy. The challenge virus is administeredintranasally in a volume of 100 microliters while the animals arelightly anesthetized with isofluorane. On day 68, serum is collected andall animals are sacrificed to collect lungs for virus titration andhistopathological analysis. Each lung is divided in two to performhistopathological analysis and virus titration. The left lungs are tiedoff and used for histopathological analysis. The lobes of the right lungare lavaged using 3 ml of Iscove's media with 15% glycerin. The lavagefluid is stored on ice until titration. In addition, nasal lavages areprepared with 2 ml (1 ml for each nare) in the same medium.

The viral load in the lung and nasal lavages is determined by plaqueassay on HEp2 cells. Cells are infected for 90 minutes with a serialdilution of the lavage samples. After removal of the inoculum, the cellsare overlaid with 2% methylcellulose in MEM-containing antibiotics.After six days of incubation at 37° C. in a COrincubator, plaques arecounterstained with 0.1% crystal violet/10% formalin solution and leftat room temperature for 24 hours.

For histopathological analysis, the left lung is perfused with 10%neutral buffered formalin. Fixed lung tissue is subsequently processedwith a microtome to produce sections that are stained with hematoxilinand eosin and scored for the degree of histopathological lesions.

Serum samples are assayed for the presence of anti-SHe- andanti-RSV-neutralizing antibodies by peptide ELISA and by amicroneutralization assay. For peptide ELISA, plates are coatedovernight at 37° C. with 2 Jig of SHe-peptide in 50 Jll of 0.1 Mcarbonate buffer pH 9.6. After coating, plates are blocked with 3% (w/v)milk powder in PBS, followed by application of three-fold serialdilutions on cotton rat sera. Retained SHe-specific cotton rat IgG aredetected using horseradish peroxidase conjugated secondary antibodiesand tetramethylbenzidine substrate. The endpoint anti-SHe peptide IgGtiter in the samples is defined as the highest dilution for which theabsorbance is at least twice as high as that of the pre-Immune serum.

Neutralizing antibody titers are determined for RSV-A and -B in 96-wellmicrotiter plates with HEp2 cells. Serial dilutions of serum samples aremixed with a fixed amount of inoculum virus. The neutralizing antibodytiter is defined as the serum dilution at which >50% reduction iscytopathic effect is observed. This cytopathic effect refers to thedestruction of cells and is determined visually after the cells arefixed with 10% neutral buffered formalin and stained with crystalviolet. The results show that the animals, vaccinated with KLH-SHe inFreund's Adjuvant develop neutralizing antibodies and are clearlyprotected, whereas the vehicle control shows no protection at all.

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1. An immunogenic composition comprising the ectodomain of the smallhydrophobic protein of a Respiratory Syncytial Virus, and a carrier. 2.The immunogenic composition of claim 1, wherein said ectodomain ispresented as an oligomer.
 3. The immunogenic composition of claim 1,wherein the ectodomain comprises SEQ ID NOs:1-3, or a variant thereof.4. The immunogenic composition of claim 1, wherein the ectodomain isgenetically linked to the carrier.
 5. The immunogenic composition ofclaim 1, wherein the ectodomain is chemically linked to the carrier. 6.The immunogenic composition of claim 1, wherein the carrier is anoligomer.
 7. The immunogenic composition according to claim 6, whereinsaid oligomer is a pentamer.
 8. The immunogenic composition of claim 1,wherein the carrier is selected from the group consisting of CartilageOligomeric Matrix Protein (comp), Lpp-56, and a virus-like particle. 9.(canceled)
 10. A method of protecting a subject against RespiratorySyncytial Virus infection, the method comprising: administering to asubject in need thereof the immunogenic composition of claim 1 forprotection against, or treatment of Respiratory Syncytial Virusinfection in the subject. 11-19. (canceled)
 20. A vaccine, comprising:the immunogenic composition of claim 1, and optionally, an adjuvant.21-22. (canceled)